The present invention relates to pharmaceutical compositions comprising calcitonin.
Calcitonin is a 32 amino acid polypeptide hormone secreted by the parafollicular cells of the thyroid gland in mammals and by the ultimobrachial gland of birds and fish. It is a potent drug for the treatment of Paget's disease, some aspects of hypercalcaemia, and for postmenopausal osteoporosis. Calcitonins of different origins, mainly salmon, pig, eel, and human are currently used therapeutically.
Human calcitonin, although considered less potent and thus required at higher concentrations or doses than salmon calcitonin, has the advantage of not generating neutralizing antibodies after prolonged administration as the salmon calcitonin does (Grauer et at. 1990, J. Bone Min. Res. 5,387-391, Levy et at. 1988, J. Clin. Endocrinol. Metab. 67,541-545 and the references therein).
In physiological saline solutions or buffers, human calcitonin is not stable, it precipitates and forms gels which consist of calcitonin fibrils. Since fibrillated calcitonin does not redissolve in physiologically compatible solutions, the calcitonin fibrils per se have not been considered for therapeutic use. Due to the fibril formation phenomenon, which was perceived to be undesirable, various steps have been adopted to avoid the problem. In particular, the injectable dosage form of human calcitonin is made up only as and when required by mixing hCT powder and the aqueous solution immediately prior to injection. This procedure is not required for salmon calcitonin which is provided in stable solution.
We have now found, surprisingly that calcitonin fibrils per se are biologically active and give a longer-time dose response than calcitonin in solution.